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Claims  |
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What is claimed is:
1. A parallel array Winchester disk drive storage system comprising:
at least three substantially standard hard disk drive storage units;
means for mounting said disk drive units side-by-side;
master controller means for controlling the operation of said disk drives
to store digital data in said drives and to route data and instructions
between a host computer and said disk drives;
means for storing data in more than one-half of said drives, and means for
storing parity check data relating to the data stored in said drives in at
least one of the other of said drives;
means for regenerating erroneous or missing data from any one of said
drives from the parity check drive data, and/or data from the other drives
in said group, in an on-line basis;
means for identifying a malfunctioning one of said drives;
means for powering down said malfunctioning drive;
means for removing any single drive unit from said system and substituting
a different drive unit into said system while the system remains on line;
means for storing digital information onto the new drive which is
substituted for the malfunctioning drive, using said regenerated data; and
said controlling means including means for storing data on said drives in
terms of successive bytes or groups of bits from the host computer being
successively applied to successive ones of said drives.
2. A storage system as defined in claim 1 wherein drive formatter means are
provided for coupling said master controller means to each of said drives.
3. A storage system as defined in claim 2 wherein said storage system
includes a housing, and wherein each disk drive and associated formatter
unit is mounted on means for guiding the drive and formatter into said
housing, and mating connector means are provided on said housing and on
each said drive and associated formatter, to automatically connect and
disconnect each said drive and formatter into the system as they are
guided into and removed from said housing, respectively.
4. A storage system as defined in claim 1 wherein said controlling means
stores data on said drives in terms of successive bytes of information of
eight bits each, being supplied to successive drives.
5. A storage system as defined in claim 1 wherein a control and signalling
panel is provided, including signal light means for indicating the status
of the system, control switches for controlling the mode of operation of
the system, alphanumeric display means for providing diagnostic
information, and a keyboard for applying control signals to the system.
6. A storage system ad defined in claim 5 wherein a removable cover for the
front of the system is provided, and means are provided for permitting
viewing of the signal lights when the cover is in place covering the front
of the drives and the control and signalling panel.
7. A storage system as defined in claim 5 wherein means are provided for
mounting said panel in front of at least one of said drives, and means are
provided for shifting said panel away from the front of any of said drives
while maintaining said panel operatively coupled to said system, to permit
removal and replacement of said drives.
8. A storage system as defined in claim 1 wherein said system includes five
drives, of which four are included in said group of drives and wherein
there is one parity drive.
9. A storage system as defined in claim 1 as defined in claim 1 further
comprising means for synchronizing the angular rotation of all of said
drives from a signal supplied by said master controller means.
10. A storage system as defined in claim 1 wherein said system includes a
housing having a height of approximately seven inches and a transverse
width of approximately seventeen inches to fit in standard nineteen inch
spacing racks, and wherein said standard disk drives are removably
mounted, side-by-side with the axes of the disk drives being generally
horizontal, within said housing.
11. A storage system as defined in claim 1 wherein said system includes
means for transferring data in parallel to the multiple drives, thereby
increasing the data rate of the system.
12. A storage system as defined in claim 1 including means for providing
SCSI commands to the master controller means from the host data processor,
and means for initially processing partial SCSI commands relating to data
transfer, and relaying head positioning instructions to the drives, to
speed up system response.
13. A method for storing data in a storage system including a plurality of
at least three substantially standard Winchester type disk drives, and a
master controller for coupling a host data processor to said disk drives,
including the steps of:
transferring data between said host computer and said drives with
successive groups of successive bits of data from said host computer being
transferred to a group of said drives including more than one-half of said
drives;
storing parity check digital information in at least one additional drive
not included in said group;
determining that a malfunction exists in one of said group drives;
regenerating data applied to said malfunctioning drive, using the parity
check digital information and/or the data stored in the remaining drives
of said group;
supplying the regenerated data to the host computer with the valid data
from other drives of said group;
physically removing the malfunctioning drive from the system and replacing
it with a new, functioning drive, while the system is kept on line; and
supplying regenerated digital information to the new functioning drive to
restore lost digital information.
14. A method as defined in claim 13 wherein the supplying of regenerated
digital information to the new drive is accomplished while the system is
on-line, between requests from the host data processor for data transfer.
15. A method as defined in claim 13 wherein commands from the host data
processor to the storage system are in a lengthy digital command format,
with data transfer information, if any, being included in an early portion
of such commands, the method including the steps of decoding the data
transfer portion of commands as they received by the storage system, and
initiating shifting of the magnetic head position of the drives to the
indicated position before the complete command had been processed, to
speed up the response of the system.
16. A method as defined in claim 13 including the additional step of
synchronizing the angular rotation of each of the drives from index
signals supplied by the master controller.
17. A parallel array Winchester disk drive storage system comprising:
at least three substantially standard Winchester type disk drive storage
units;
means for mounting said disk drive units adjacent one-another;
master controller means for controlling the operation of said disk drives
to store digital data in said drives and to route data and instructions
between a host computer and said disk drives;
means for storing data in a group of more than one-half of said drives, and
means for storing parity check data relating to the data stored in said
group of drives in at least one of said drives not included in said group
drives;
means for regenerating erroneous or missing data from any one of said group
of driven from the parity check drive data, and data from the other drives
in said group;
said controlling means including means for storing data on said drives in
terms of successive bytes or groups of bits from the host computer being
successively applied to successive ones of said group of drives; and
means for synchronizing the angular rotation of all of said drives from a
signal supplied by said master controller means.
18. A storage system as defined in claim 17 wherein said controlling means
stores data on said drives in terms of successive bytes of information of
eight bits each, being supplied to successive drives in said group of
drives.
19. A storage system as defined in claim 17 wherein a control and
signalling panel is provided, including signal light means for indicating
the status of the system, control switches for controlling the mode of
operation of the system, alphanumeric display means for providing
diagnostic information, and a keyboard for applying control signals to the
system.
20. A storage system as defined in claim 19 wherein means are provided for
mounting said panel in front of at least one of said drives, and means are
provided for shifting said panel away from the front of any of said drives
while maintaining said panel operatively coupled to said system, to permit
removal and replacement of said drives.
21. A storage system as defined in claim 17 wherein said system includes
five drives, of which four re included in said group of drives and wherein
there is one parity drive.
22. A storage system as defined in claim 17 including means for providing
commands to the master controller means from the host data processor, said
commands having a lengthy format including data transfer information, if
any, in an early portion of said command, and means for initially
processing the portion of the commands relating to data transfer, and
relaying head positioning instructions to the drives, to speed up system
response.
23. A parallel array Winchester disk drive storage system comprising:
at least three Winchester type disk drive units;
means for mounting said disk drive units adjacent one-another;
master controller means for controlling the operation of said disk drives
to store digital data in said drives and to route data and instructions
between a host computer and said disk drives;
means for storing data in a group of more than one-half of said drives, and
means for storing parity check data relating to the data stored in said
group of drives in at least one of said drives not included in said group
of drives;
means for regenerating erroneous or missing data from any one of said group
of drives from the parity check drive data, and data from the other drives
in said group;
said controlling means including means for storing data on said drives in
terms of successive bytes or groups of bits from the host computer being
successively applied to successive ones of said group of drives; and
means for providing commands to the master controller means from the host
data processor, said commands having a lengthy format including data
transfer information, if any, in an early portion of said command, and
means for initially processing the portion of the commands relating to
data transfer, and relaying head positioning instructions to the drives,
to speed up system response.
24. A parallel array Winchester disk drive storage system comprising:
at least three Winchester type disk drive units;
means for mounting said disk drive units adjacent one-another;
master controller means for controlling the operation of said disk drives
to store digital data in said drives and to route data and instructing
between a host computer and said disk drives;
means for storing data in a group of more than one-half of said drives, and
means for storing parity check data relating to the data stored in said
group of drives in at least one of said drives not included in said group
of drives;
means for regenerating erroneous or missing data from any one of said group
of drives from the parity check drive data, and data from the other drives
in said group;
said controlling means including means for storing data on said drives in
terms of successive bytes or groups of bits from the host computer being
successively applied to successive ones of said group of drives;
said system including drive formatter means for coupling said master
controller means to each of said drives; and
said system including a housing, and each disk drive and associated
formatter unit being mounted on means for guiding the drive and formatter
into said housing, and mating connector means on said housing and on each
drive and associated formatter, to automatically connect and disconnect
each said drive and formatter into the system as they are guided into and
removed from said housing, respectively.
25. A system as defined in claim 24 including means for replacing any
single drive in said system while the system remains on line.
26. A storage system as defined in claim 24 wherein a control and
signalling panel is provided, including signal light means for indicating
the status of the system, control switches for controlling the mode of
operation of the system, alphanumeric display means for providing
diagnostic information, and a keyboard for applying control signals to the
system.
27. A storage system as defined in claim 26 wherein means are provided for
mounting said panel in front of at least one of said drives, and means are
provided for shifting said panel away from the front of any of said drives
while maintaining said panel operatively coupled to said system, to permit
removal and replacement of said drives.
28. A storage system as defined in claim 24 wherein said system includes
five drives, of which four are included in said group of drives and
wherein there is one parity drive.
29. A storage system as defined in claim 24 as defined in claim 1 further
comprising means for synchronizing the angular rotation of all of said
drives from a signal supplied by said master controller means.
30. A storage system as claimed in claim 24 including means for providing
commands to the master controller means from the host data processor, said
commands having a lengthy format including data transfer information, if
any, in an early portion of said command, and means for initially
processing the portion of the commands relating to data transfer, and
relaying head positioning instructions to the drives, to speed up system
response.
31. A parallel array Winchester disk drive storage system comprising:
at least three substantially standard Winchester type disk drive storage
units;
means for mounting said disk drive units adjacent one-another;
master controller means for controlling the operation of said disk drives
to store digital data in said drives and to route data and instructions
between a host computer and said disk drives;
means for storing data in a group of more than one-half of said drives, and
means for storing parity check data relating to the data stored in said
group of drives in at least one of said drives not included in said group
drives;
means for regenerating erroneous or missing data from any one of of said
group of drives from the parity check drive data, and data from the other
drives in said group;
said controlling means including means for storing data on said drives in
terms of successive bytes or groups of bits from the host computer being
successively applied to successive ones of said group of drives;
means for synchronising the angular rotation of all of said drives from a
signal supplied by said master controller means; and
drive formatter means for coupling said master controller means to each of
said drives.
32. A storage system as defined in claim 31 wherein said storage system
includes a housing, and wherein each disk drive and associated formatter
unit is mounted on means for guiding the drive and formatter into said
housing, and mating connector means are provided on said housing and on
each said drive and associated formatter, to automatically connect and
disconnect each said drive and formatter into the system as they are
guided into and removed from said housing, respectively. |
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Claims |
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Description |
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FIELD OF THE INVENTION
This invention relates to digital storage systems using a plurality of
Winchester disk drives.
BACKGROUND OF THE INVENTION
In the field of digital data storage systems, five and one-quarter inch
Winchester disk drives are widely used, and their dimensions have been
standardized at 3.25 inches by 5.75 inches by 8.0 inches. The storage
capacity of these units has been increasing, with the 1500 series units
made by Micropolis, the assignee of the present invention, now having a
storage capacity above 350 megabytes; and it is expected that this
capacity will at least double in the relatively near future. Incidentally,
a "byte" of digital information includes eight binary digits or "bits" of
information, a megabyte is a million bytes or 8,000,000 bits, and one
gigabyte is a billion bytes or eight billion (8,000,000,000) bits of
digital information.
With the relatively high production quantities of five and one-quarter inch
Winchester disk drives, the cost per megabyte has come down to a moderate
level. However, for higher storage capacities, coupled with higher data
rates, typically accomplished by 101/2 and 14 inch parallel head
Winchester drives, the cost per megabyte has been substantially higher, in
the order of at least two or three times the cost per megabyte of the
individual five and one-fourth inch drives.
Accordingly, a principal object of the present invention is to provide a
large scale, high data rate storage system having a substantially lower
cost per megabyte than the systems which are currently available.
Incidentally, proposals have been made heretofore to use two or more
Winchester type drives together, to provide higher reliability or a larger
storage capacity. For example, reference is made to U.S. Patent Defensive
Publication No. T932,005 dated Mar. 4, 1975, U.S. Pat. No. 3,623,014,
granted Nov. 23, 1971 and to European Patent Application Nos. 85 4004 93.4
published Oct. 2, 1985, 156,724. The first two references cited above
essentially use a second Winchester drive to duplicate the stored
information, to provide increased reliability. Concerning the European
Patent Publication, it appears to include a superficial disclosure of a
system in which it is proposed that several Winchester drive storage units
be employed, and in which successive bits of incoming data are to be
routed to the different storage units. It is also noted that the various
Winchester drive units are not synchronized, thereby adding additional
delays to data access times.
As compared with the foregoing prior art arrangements, principal objects of
the present invention are to reduce the data access time, and to provide a
reliable, high capacity, high data rate, and relatively inexpensive
storage system.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, at least three standard
commercially available disk drives are operated together, to appear as one
singular unit using a data formatter for each drive and a master
controller, and with successive bytes (or groups of bits) of information
being routed to all except one of the successive disk drives, and with one
drive serving as a parity check storage unit.
An important feature of the invention is the parallel transfer of data to
the multiple drives, thereby increasing the data rate of the system.
In accordance with another aspect of the invention, all of the disk drives
are operated in synchronism, with spindle synchronization circuitry from
the master controller providing synchronization signals to each drive, so
that all of the disks rotate substantially together, and failure of any
one drive not affecting synchronization of the other drives.
In accordance with a further aspect of the invention, all of the disk
drives may be physically mounted in a housing, side-by-side on tracks,
with a drive formatter associated with each drive, and the combination
being slidable in and out of mating connectors in the housing, so that the
individual drives and associated drive formatters may be easily replaced
and a new unit put into operation by pulling one of the units out and
sliding the new unit into its place.
Further, control and signal actuation circuitry is provided to indicate
fault conditions, and to permit continued operation of the system even
with one drive unit completely disabled, through the use of parity
information from the parity check drive. Circuitry is also provided for
permitting the removal of a failed drive and the substitution of a new
drive without interruption of operation of the system.
Another feature of the invention permits full regeneration of data when a
new drive is substituted for a failed drive, either with the system
remaining "on-line", or with the system dedicated to data regeneration.
A further aspect of the invention involves the coupling of the host
computer to the master controller of the storage system of the invention,
using a standard SCSI bus and data system, wherein delay in coupling the
host computer is minimized by initial processing of partial SCSI commands,
relating to data transfer, and relaying head positioning information to
the drives, instead of delaying all action until the full SCSI command is
processed.
The signal lights, alpha-numeric display and control keyboard constitute
another feature of the invention. In one illustrative embodiment of the
invention, the complete storage system has a front cover, and the signal
lights, which may be light-emitting diodes (LEDs), are visible through the
front cover. If the system is working properly with no faults, the signal
light display will so indicate. However, if a fault should occur, the
front bezel or cover of the system may be removed, to expose the control
panel. To conserve space, the control panel, the signal lights, and the
associated printed circuit board may be pivotally mounted to swing out of
the way to permit the replacement of drives. Alternatively, the control
panel may be on the front cover of the unit, or in an alternative location
where it will not interfere with the replacement of drives.
The control panel may include a digital keyboard for providing test
instructions to the system when it is in the fault diagnostic mode.
An LED display may also be provided on the control panel to visually
indicate the nature of faults, the results of diagnostic tests, and
similar information.
Advantages of the system of the present invention include:
1. High reliability, with a mean time to failure for the entire system
being estimated at 65,000 hours. For the drive matrix, excluding the power
supply and the master controller, the mean time before failure (MTBF) is
estimated at 1,400,000 hours.
2. Rapid throughput of information resulting from spindle synchronization
of the drives.
3. Low cost per megabyte of storage, resulting from the use of standard
mass produced 51/4 inch drives.
4. Rapid response to host computer instructions resulting in part from
early response to initial data transfer information included in SCSI
format instruction.
5. Capability of replacing a failed or malfunctioning drive and
regenerating data while the system is on-line, without interrupting
operation.
6. The system has a relatively high data rate, of 5 megabytes per second
when a five drive system configuration is employed, and 10 megabytes per
second when a ten drive system configuration is used.
7. The system provides natural encryption or encoding, with no extra cost
or penalty, as the information on each drive is only a fraction of the
complete data, and is unintelligible per se.
Other objects, features, and advantages will become apparent from a
consideration of the following detailed description, and from the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a system illustrating the principles of the
present invention;
FIGS. 2A, and 2B together form an exploded view showing one illustrative
physical configuration of the system of FIG. 1;
FIG. 3 is an enlarged view of the control and signaling panel included in
the system of FIGS. 1 and 2;
FIG. 4 is a showing of the computer of FIGS. 1 and 2, with the front panel
and the control panel removed, and one of the five Winchester drive and
formatter units pulled part-way out of the system for replacement;
FIGS. 5A through 5E together form a circuit diagram showing the control
wiring for the signal lamps and related circuitry of the control panel;
FIGS. 6A and 6B together form a block circuit diagram of a channel
formatter associated with each of the drive units;
FIGS. 7A through 7F constitute a circuit diagram of the data path circuitry
of the master controller;
FIGS. 8A and 8B together form a block diagram for another major portion of
the master controller, involving the master, controller CPU and associated
input and output circuitry;
FIGS. 9, 10 and 11 constitute additional circuitry forming part of the
master controller;
FIG. 12 is a servo loop functional diagram indicating the mode of operation
of the spindle synchronization circuitry;
FIG. 13 is a block circuit diagram showing the mode of operation of the
spindle synchronization circuitry;
FIG. 14 is a diagram representing the "fail-safe" mode of operation of the
system; and
FIG. 15 is a program diagram showing the "fast seek" technique for speeding
up the transfer of data between the host computer and the storage system
of the present invention.
DETAILED DESCRIPTION
Referring more particularly to the drawings, a host computer 12 is coupled
to the master controller 14 forming part of the system of the present
invention, by a SCSI interface 16. Incidentally, the letters "SCSI" stand
for Small Computer System Interface, and this is a well known industry
standard. At the far right-hand side of FIG. 1 are a series of standard
commercially available Winchester drives 18, 20, 22, 24 and 26. These
drives may, for example, be 51/4 inch disk drives of the 1500 Series,
manufactured by the assignee of the present invention, Micropolis
Corporation, 21329 Nordhoff Street, Chatsworth, Calif. 91311. Associated
with each of the five drives is a channel formatter 28 and associated
spindle synchronization circuitry 30. Interconnecting the channel
formatters and the drives is a series of ESDI interface circuits 32.
Coupling the master controller 14 to the individual channel formatters 28
is a master/channel bus 34, and a spindle reference signal circuit 36.
With regard to the spindle synchronization circuitry, it may be noted that
each of the drives 18, 20, 22, 24 and 26 are all separately synchronized
to a spindle reference signal supplied to the circuits 30 on lead 36 from
the master controller 14, and none of the drives is separately coupled or
synchronized with the other. As a result of the fact that the drives are
all independently synchronized to the master synchronization pulses
arriving on the lead 36, the failure of any one drive does not affect the
synchronization of the other drives. Incidentally, this type of
arrangement is to be preferred over arrangements wherein one of the drives
is employed as a master to which the other drives are slaved, so that the
entire system does not go down in the event that the master drive should
fail.
It is also noted that, in handling data received from the host computer 12,
the master controller splits up the data into successive bytes, each
including eight bits of information, and routes the successive bytes of
information through the channel formatters 28, with the first byte being
applied to drive 18, the second byte being applied to drive 20, the third
byte of digital information being applied to drive 22, and the fourth byte
of information being applied to drive 24. A parity check byte of eight
bits is also formed, and this is applied to drive 26, which is the parity
check drive. The fifth byte of information is routed to drive 18, and the
sequence is continued in this manner. The data is supplied between the
individual channel formatters and the master controller in parallel, and
this permits a high data rate for the storage system.
Attention will now be directed to FIGS. 2A, 2B and FIGS. 3 and 4, which
show certain physical aspects of the present system. With regard to
dimensions, the standard 19 inch electrical equipment rack size actually
has approximately 17.81 inches available between the supporting frame
members. Further, the modular vertical size involves increments of 13/4
inches. In the present case, with standard drives being 53/4 inches in
width in their normal horizontal orientation, by orienting the drives with
each of five drives being on what would normally be their sides, the total
vertical extent of the housing may be 7 inches, or four times the modular
distance of 13/4 inches. In addition, five drives, each having a thickness
of 3.25 inches, may be fitted within the 17.81 inch distance available
with standard 19 inch racks.
Now, referring to FIGS. 2A and 2B and of the drawings, an exploded view of
the physical configuration of the system is presented. More specifically,
the system includes a main housing 42 provided with side rails 44 which
interfit with the mounting rails 46 which would be secured to the 19 inch
rack. The transverse dimension of the housing 42 without the tracks is
approximately 171/4 inches, so that, with the tracks 44 and 46 on either
side, the housing 42 may be mounted in the 17.81 inches available between
the frame members of a 19-inch rack.
Turning to the other parts which appear in FIG. 2A, the master controller
circuit board is shown schematically by the board bearing reference
numeral 14, and the top cover of the unit is shown at reference numeral
50. The power supply unit 52 is mounted within the space 54 to the rear of
the housing 42. The rear closure 56 of the housing 42 is provided with
fans 58 and associated grilles 60 and supporting frame members 62.
Referring to FIG. 2B, one of the five drive units 18, together with its
associated channel formatter 28 embodied in circuit boards secured to the
rear of the drive 18, is shown. The drive and its associated formatter 28
are mounted within the subassembly 66 which is provided with upper and
lower tracks, with the upper track 68 being visible in FIG. 2B. Mating
upper and lower tracks 70 and 72 are secured within the housing 42 so that
all five of the subassemblies 66, 74, 76, 78 and 80 may be mounted
side-by-side toward the front of the housing 42, all as shown to better
advantage in FIG. 4 of the drawings. At the front of each of the
subassemblies, such as the subassembly 68, a front cover plate 82 is
provided, along with a handle 84 which may be employed in pulling the
individual subassemblies out, and replacing them, as indicated
schematically in FIG. 4 of the drawings.
Extending outwardly from the rear of each of the subassemblies 66, 74,
etc., is a printed circuit board having a rear edge which forms a male
connector 86. As each subassembly, such as the subassembly 66 is slid into
the housing 42, guided by tracks such as those indicated by reference
numerals 68, 70 and 72, the male connector 86 mates with a floating female
connector 88 which is mounted within the housing 42 for automatic
self-alignment as the male connector 86 moves to the rear within housing
42. Cables 90 and 92 couple the drive 18 and the channel formatter 28 to
the master controller 14 and to the power supply 52.
A signal light, control panel, and visual display assembly, indicated by
the reference numeral 96 is mounted by the hinge 98 to the flange 100
which appears at the front right-hand side of the housing 42, as shown in
FIG. 2A. The assembly 96 includes a support plate 102, a printed circuit
board 104 which carries a liquid crystal display 106, having the
capability of displaying two rows of alphanumeric characters of 16
characters each. In addition, the assembly 96 includes the write protect
switch 108 and the cable 110 which couples the circuitry to the master
controller. A series of light-emitting diodes 112 are also provided for
signaling purposes, and the switch panel 114 permits manual control of the
system, and the entering of control signals for diagnostic and other
functions, in the event of faults occurring in the system. Incidentally,
an enlarged view of the control panel is set forth in FIG. 3 of the
drawings.
The front cover 116 of the system is shown to the lower right in FIG. 2B,
and this cover has a series of openings 118 through which the
light-emitting diodes are clearly visible, so that the status of the
system may be readily determined. If the system is "on line" and operating
properly, there is no need to remove the cover 116. However, if the LED
displays visible through the openings 118 indicate fault conditions, as
indicated by the legends adjacent the openings, the cover 116 is removed,
and appropriate diagnostic steps may be taken.
As will be developed in greater detail hereinbelow, the present system is
unique in the capability of being able to have one of the drive and
channel formatter subsystems removed, while the overall storage system is
still on-line and performing its normal function. FIG. 4 indicates
schematically how one drive and formatter unit could be easily removed by
grasping the handle 84 and pulling the unit out and merely substituting a
new subsystem including a drive and formatter in its place. With the
self-aligning male and female edge connectors of the type discussed
hereinabove relative to reference numerals 86 and 88, (see FIG. 2B), once
the new unit has been slid into position to replace the failed or
malfunctioning subsystem, the electrical connections to the channel
formatter and drive are automatically closed so that it may be immediately
powered up. Further, as discussed hereinbelow, the data previously applied
to the failed drive may be reconstituted in a relatively brief period of
time, using the information on the other three data drives, and that from
the parity drive.
The overall mode of operation of the control panel, including the display,
the signal lights, and the various switches will now be considered in
connection with FIG. 3 of the drawings, and thereafter, the implementing
electrical circuitry and program functions will be considered in some
detail in connection with the additional figures of the drawings.
Referring now in detail to FIG. 3, the individual light-emitting diode
signal lights included at 112 are the LED 122, designated "POWER"; the LED
124 designated "READY"; the LED 126, designated "ON-LINE"; the LED 128,
designated "DIAGNOSTIC"; the LED 130, designated "RESTORING"; and LED 134,
designated "FAULT". In addition, the front panel includes the write
protect switch 136 which includes an internal LED 138 to indicate when the
write protection function is in effect, precluding the writing of
information onto any of the disk drives, when the "WRITE PROTECT" switch
is pushed in. The key pad portion 114 of the panel includes the numerical
key pad section 140, and four additional switches, with the "ENTER" switch
being designated by the reference numeral 142, the "RESTART" switch being
designated by reference numeral 144, the "ON-LINE DIAGNOSTIC" switch being
designated by the reference numeral 146, and the final "RESTORE" switch
being identified by reference numeral 148.
Now, assuming that the system is on-line and operating, the top three
signal lights 122, 124, and 6 will be energized and lit, and the liquid
crystal display 106 will display the message "SYSTEM RUNNING". While the
system is on-line, the master controller will scan the state of the front
panel switch status registers for inputs. The "WRITE PROTECT" switch 136,
the "ON-LINE DIAGNOSTIC" switch 146 and the "RESTORE" switch 148 are the
only inputs to which the master controller will respond while it is in the
"ON-LINE" state. The number keys 140, the "RESTART" switch 144, and the
"ENTER" switch 142 will all be ignored.
The Write Protect switch 136 is a "PUSH-ON-PUSH-OFF" two position switch.
When the switch is pushed in, the LED 138 will be lit and writing to the
drives will be inhibited. When the switch is out, the LED 138 will be off,
and data may be written to the drives.
The "On-Line/Diagnostic" switch 146 controls the mode of operation of the
system. Pressing this switch 146 while the system is on line, will change
the system to the diagnostic mode, and no further commands will be
recognized or accepted on the SCSI bus 16 coupling the master controller
to the host computer. The "On-Line" LED 126 will be turned off and the
"Diagnostic" LED 128 will be lit.
Pressing the "Restore" switch 148 will begin a restore operation on a
channel that was powered down by the system to a fault. This function can
be performed if one and only one channel drive has failed, and is normally
accomplished after a module including a new drive and associated formatter
have been substituted for a failed drive. The "Restoring" LED 130 will be
lit until the data previously stored or intended to be stored in a failed
drive has been completely restored. This function may be carried on during
normal operation, in time intervals when the host computer is not
accessing the storage system; or alternatively, the system may be fully
shifted over to the restoring mode, and the system taken off line, in
which case the full restoring of a substituted drive might take in the
order of 15 minutes to a half hour.
When it is desired to restore data onto a newly substituted drive unit
rapidly, on a dedicated basis, the "ON-LINE DIAGNOSTIC" switch 146 is
actuated, and then the "RESTORE" switch 148 is actuated. However, if the
"RESTORE" switch 148 is actuated when the system is on line, then the
master controller will perform restore functions when the host computer
makes no demands. When a command is received from the host computer, under
these conditions, the master controller will store the command momentarily
while completing a sector of restoring, and then switch over to normal
storage operation under control of the host data processor. Upon the
occurrence of the next time interval, when the host computer makes no
demands upon the storage system, the master controller will resume
restoration of data in the newly substituted drive unit, with data
regeneration being accomplished as discussed below in connection with
FIGS. 7A through 7F.
Concerning the display 106 and the signal lights 112, when the system is
operating perfectly, the top three signal lights 122, 124, and 126
involving (1) power, (2) ready, and (3) on-line, will be lit, and the
other LEDs in the array 112 will be off. In addition, the display 106 will
bear the legend, "SYSTEM RUNNING" Normally, under these conditions, the
cover 116 will be in place, and the LED array 112 will be visible through
the openings 118 in the cover 116. The legends shown in FIG. 3 are of
course also repeated on the cover 116. As long as the upper three LEDs are
lit, and the lower three LEDs are not energized, there is no need to
remove the cover 116.
The system of the present invention is operative, even when the system
develops certain faults, even to the extent of one of the drive modules
having completely failed. With various minor malfunctions occurring the
system, the "Fault" LED 134 will be energized, and either turned on
continuously, or will be blinked, in some cases in combination with
blinking of the "On-Line" LED 126.
In Appendix I attached to this patent application is a Table setting forth
the pattern of LED energization, and the message which will appear on the
LCD display 106, when various faults occur. Thus, for example, the third
entry in Appendix I indicates that the power and the on-line LED's 122 and
124 are "on", but the "Ready" and the "Fault" LED's 124 and 134 are
blinking. In addition, the LCD message will state "CH#.sub.-- ER:03 and
"REPLACE CH #.sub.-- ". As indicated in the description, the fault which
has been found is that "No index or sector signal is found; error channel
will be powered down". In practice, when the operator sees the "Ready" and
the "Fault" signals blinking, the cover 116 of the storage system will be
removed, so that the LCD display 106 may be observed. Once the operator
observes that a particular channel must be replaced, this action is
accomplished, using the handles 84, as shown in FIGS. 2B and 4.
Incidentally, in order to pull out either of the two right-hand drives,
the display and switch panel must be pivoted forward, hinging about the
hinge 98 as shown at the upper right-hand FIG. 2B.
Following the substitution of a new drive module including standard drive
and the associated formatter, the system may continue on-line, with
restoring being accomplished during intervals when the host computer is
not accessing the storage system, as mentioned above. Alternatively, the
system may be taken off-line, and the information which either had been
stored or had been intended for storage on the failed drive may be entered
into the newly replaced unit.
In other cases, when the system has a malfunction, but not a failed drive,
it may be appropriate to undertake diagnostic tests to ascertain the
problem.
The front panel diagnostic is an off-line series of programs which will
perform basic testing of the system. Their main purpose is to verify the
pass/fail status of the various components of the system at as low a level
as possible to identify failed components and restore the system to full
operation as quickly as possible. The tests available through the front
panel diagnostics are designed to test specific features. These tests will
be on a lower level than the system diagnostic tests run from the host
computer. All diagnostic functions are input through the numeric keypad
140 on the front panel and all results are displayed on the 32 character
LCD display 106, or in the LEDs in the array 112. All tests are run
individually as they are selected, with no preselect, or initialization,
as is customary in system diagnostics run from the host computer.
Testing is in two main areas, the master controller, and the channel
controller/disk drive assemblies. The master controller tests include
separate tests for the major hardware blocks, including the sequencer, the
"first-in, first-out" (FIFO) buffer store, the random access memory (RAM)
and the interface controller. The channel controller tests will involve
low level commands to the channels using the master controller to channel
formatter interface.
Control of the master controller will be passed on to the front panel
diagnostics, when the on-line/diagnostics switch 146 is actuated. The LCD
106 is then cleared and a "?" is displayed as a prompt for diagnostic
function code entry. There will be no changes in the status of the drives
or the LEDs. After initial setup is complete, the diagnostic will be in an
idle loop, waiting for input from the keypad 140.
All test function codes are two digit codes. The digits will be echoed or
displayed, on the LCD as they are entered. An attempt to enter a digit
that does not form a valid diagnostic function code will not be accepted.
After a valid function code has been entered, the test name will be
displayed in the LCD following the code. Pressing the "Enter" switch 142
will cause the execution of the test. Pressing the "Restart" switch 144
before the "Enter" s | | |
